Friday evening, just before leaving the office to pick-up the kids after their first week back in class, Matthew Champion (aka @matthewchampion) sent me an email, asking for more details. He wanted to know if I did produce those graphs, and if he could mention then, in a post. The truth is, I have no idea who produced those graphs, but I told him one can easily reproduce them. For instance, for the cities, in R, use